Two-Step Encapsulation for IC Heat Spreader Filler Distribution
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Solution Overview
Problem
The use of low-k interlayer dielectric materials in electronic devices leads to weak adhesion issues, causing ILD crack or delamination, particularly during temperature cycling tests, due to non-uniform distribution of mold compound fillers in the die corner opposite the mold gate, where the heat spreader obstructs mold compound flow during transfer molding.
Innovation Solution
A two-step encapsulation method is employed, where a first encapsulating layer is formed over the IC die and bond wires, followed by positioning a heat spreader above it, and then a second encapsulating layer is formed to embed the heat spreader, ensuring uniform material distribution and reducing filler loss in the corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat spreader is positioned on the substrate during transfer molding, then heat dissipation performance is improved, but mold compound flow is obstructed resulting in non-uniform filler distribution
Solution Approach 1:
The patent applies preliminary action by forming the first encapsulating layer covering the IC die and bond wires before positioning the heat spreader. This preliminary encapsulation protects the underlying structures and allows subsequent molding material to flow uniformly around the heat spreader, eliminating filler distribution non-uniformity while maintaining heat dissipation functionality.
Solution Approach 2:
The patent segments the encapsulation process into two distinct steps: first forming an encapsulating layer over the IC die and bond wires, then forming a second encapsulating layer after positioning the heat spreader. This segmentation allows each step to optimize for its specific function, ensuring both heat dissipation and uniform filler distribution.
2Speed
If low-k interlayer dielectric material is used to reduce interconnect delay, then signal transmission speed is improved, but adhesion strength decreases causing ILD crack or delamination
Solution Approach 1:
The patent uses composite materials by combining the low-k interlayer dielectric material with properly distributed mold compound fillers through the two-step encapsulation process. The uniform filler distribution achieved by this method creates a composite structure that maintains the low adhesion loss characteristics of low-k material while providing mechanical reinforcement to prevent cracking and delamination.
Solution Approach 2:
The patent applies local quality by ensuring uniform distribution of mold compound fillers throughout the encapsulation material, particularly in corner regions. This uniform local composition prevents weak adhesion zones that would otherwise form, maintaining consistent protective properties across the entire device while preserving the low-k material's signal transmission advantages.
3Device complexity
If transfer molding is performed with heat spreader in place, then heat dissipation structure is integrated, but filler loss increases in die corner opposite mold gate
Solution Approach 1:
The patent applies preliminary action by completing the first encapsulation layer before positioning the heat spreader and performing the second molding. This preliminary encapsulation prevents molding material from directly contacting and adhering to the heat spreader surface, eliminating filler loss in critical regions while still achieving integrated heat dissipation structure through the second encapsulation step.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method decreases the failure rate of electronic devices by reducing ILD crack and delamination, enhancing the reliability of low-k interlayer dielectric materials in high wire density packaging.
Implementation Method 1
curing the first encapsulation material
Data Source
AI summary
A method of making an electronic device may include positioning an integrated circuit (IC) die on an upper surface of a grid array substrate having connections on a lower surface thereof and coupling respective bond pads of the IC die to the grid array with bond wires. The method may also include forming a first encapsulating layer over the IC die and bond wires and positioning a heat spreader on the substrate above the first encapsulating layer after forming the first encapsulating layer. The method may further include forming a second encapsulating layer over the first encapsulating layer and embedding the heat spreader in the second encapsulating layer.